‘That’s no good. It’s a hundred and fifty miles away,’ Hoskins said. ‘Could it be a cloned plate?’

‘Maybe,’ Dodd said. ‘Anyway, this vehicle was picked up four times on our back roads network.’ He turned to a female officer across the room. ‘Sally, have you managed to overlay the Range Rover’s movements onto a cell site analysis for the Hallam phone?’

‘I have.’ Research Intelligence Officer Sally Rickard asked for the lights to be dimmed so she could project a map from her laptop. ‘As you can see, we cover everywhere from Woking and Lacey Dutton in the west of the county, right the way across to Chipstead, near Gillard’s home, and Caterham in the east. Unfortunately, we only have a very few data points. The red dots are the ANPR hits, and the blue squiggles are the cell site paths for the phone. The question we have to ask ourselves is this: what is the probability that this phone was in the vehicle? Now apart from the Westmeare bus stop, which is an almost exact coincidence of the two colours in time and place, all the others have a time and geography disconnect. The good news is that there is not a single impossibility.’

A hand went up at the back. ‘Sorry to be dim but—’

‘Right, let me explain,’ Rickard said. ‘If we had a cell site flash in Woking at, say, noon, and an ANPR hit forty miles away in Caterham five minutes later, I think we can all agree that would be an impossibility. So all of our observations show the phone may have been in the vehicle we’ve identified. We’d need many more observations to prove the thesis, but it is the most likely.’

‘That is all very impressive,’ said Otara, who was sitting on a desk close to one of the whiteboards. ‘But the working assumption of this analysis is that the phone remains with the vehicle.’

‘That’s implicit,’ Rickard said.

‘But if you cast your mind back to the earliest events, and the tracking of Beatrice Ulbricht, we know the phone was separated from the individual for long enough to waste a week of police time looking in London for her, when she was actually here in Surrey.’

‘But unlike that case, I don’t think our suspect knows we have this phone trace,’ Rickard said.

‘Don’t bet on it,’ Otara replied. ‘He’s smart.’ He turned back to the other officers. ‘What’s the latest on the cold case?’

Rainy Macintosh put up her hand. ‘I’m waiting for DI Perry to forward me some historic documents. He’s off tonight—’

‘Off? Why now of all days?’ Otara asked.

‘It’s compassionate leave, family trouble, apparently. DCS Dobbs said it was okay, because this is the least urgent part of the case.’

‘Speaking of which, where is Dobbs?’ Otara asked.

‘Och, I think he’s tucked up in bed,’ Macintosh replied.

Perry had agreed to stay out of the marital bedroom, and he certainly wasn’t going to sleep in his daughter’s room knowing what had gone on in that bed. The sofa downstairs was comfortable, but he had a sudden image of Halliday making use of it with Vanessa. He swore softly to himself as he padded about, realising that Halliday had not only screwed everybody in the Perry family bar him, but may well have used every piece of soft furniture to do it on. That left the futon in the box room, which also doubled as his study. Seeing as it was too cramped for sleep, it was an unlikely choice for sex. That’s where he would lie.